This time three years ago I was getting my application together for the MSc in Science Communication at DCU. Part of the application was to write an essay about a scientific subject of our choice. I chose to write about Pluto.
Although I totally accept why it's no longer a planet, I still feel a little loss in that part of my internal solar system. So this week, as NASA flew by Pluto that inner fangirl rejoiced and poured over the photos, retweeted the cartoons. Ah Pluto, what secrets you have to share with us.
Anyway. Here's my 2012 essay:
When I was a kid there were nine planets in our solar system. As far as I was aware, there had always been nine planets, and there would always be nine planets.
And then in 2006 we lost Pluto.
I am still heartbroken. No really, I have t-shirts that mourn the loss. I know that the entity formally known as the PLANET Pluto is still out there orbiting the sun the way it always did, but it seems, at least to me, tragically altered.
How could this happen? How could the bedrock of my understanding of our solar system be so flawed?
In searching for that answer I discovered far more about our little corner of the universe than I ever expected to.
Up until the 1600s people knew of only six planets, the five wanderers: Mercury, Venus, Mars, Jupiter and Saturn and Earth, the sixth planet, although it was believed by many that the known universe revolved around Earth. All this changed with Galileo and his heretical support of the theory of Heliocentrism.
While observing the night sky through his telescope, Galileo found objects orbiting a distant planet - the four Galilean moons of Jupiter. If the moons were orbiting another planet, then our planet was not special. The universe did not revolve around us. In the following century improvements to the quality of telescopes meant that more astronomers were finding more planets in the Solar System. Some of these planets are well known today:
Uranus was found in 1781 by William Herschel, and was the very first planet to be found by a telescope. It’s (to quote George Hrab) far, like really far, away. It takes 84 years to complete one orbit of the sun.
Neptune was discovered by maths. It’s true. Astronomer’s use maths to predict the orbit of a planet, and when, in the mid 1800’s, Uranus did not follow its expected path, the French mathematician Le Verrier thought it might be another planet’s mass throwing it off (not actually throwing it off its orbit, but influencing the path of the orbit). No-one believed him. Well the French astronomer’s didn’t believe him so he went to the Germans – namely Johann Gottfried Galle at the Berlin Observatory. Galle looked at the maths, pointed his telescope at the right patch of the night sky and pretty much immediately found Neptune. Approximately 17 days later he found the moon Triton.
Take that, French astronomers of the 19th Century.
So we have eight of our nine planets: Mercury, Venus, Earth, Mars, Juptier, Saturn, Uranus and Neptune. What of the ninth?
Well the first ninth planet was actually the eighth. In January 1801, the planet Ceres was discovered by Giuseppe Piazzi. And in 1807 the ninth planet Vesta was found.
I don’t know about you, but I had always known these to be asteroids. However, like lowly Pluto, these two orbiting bodies once held the status of Planet. Ceres held on for nearly 50 years before being demoted. Due to the large volume and relatively small size of these objects a new classification of Asteroid was invented. And once more we were back to eight planets.
The search was on for a proper ninth planet. And finally in 1930 Clyde Tombaugh observed an object moving at the outside edge of the observable solar system, an object that was moving too slowly to be an asteroid: Pluto.
For nearly 90 years Pluto clung to its status as a planet, despite astronomers muttering that it was too small (smaller even than our moon). But in 1992, David Hewitt and Jane Lau discovered 1992 QB1, the first object of the Kuiper Belt, the first proper nail in the coffin for Pluto’s planetary status. By 1996 over 30 more objects had been found in the same region of space as 1992 QB1. The final nail didn’t arrive until 2003 when Eris, the “tenth” planet, was located far out in the distant reaches of space. So far out, in fact, that its entire atmosphere collapses and freezes to the surface.
But was Eris a planet? And if Eris wasn’t a planet, then what was Pluto?
In August 2006, the world’s foremost astronomers met to discuss this very question. At the end of that meeting a new category was announced. Eris and Pluto were not big enough to be considered proper planets, but were too interesting to be mere asteroids. They would be classed as Dwarf Planets.
So the Solar System is as it always was, though our understanding of it has grown and changed. In 1599 there was no Uranus, Neptune, Pluto or Eris. There were no moons around other planets. The universe revolved around the Earth.
But scientists and astronomers went out and explored space. People put their lives on the line for the truth. The received wisdom was questioned, and then amended to reflect newer information.
Pluto is an example of science in action, which I think, in the end, is better than just being a planet.